This invention relates to agents which decrease the immune response, i.e., immunosuppressive agents.
Cyclosporin A (CsA), a cyclic undecapeptide of fungal origin, and FK506, a neutral macrolide of fungal origin, are potent immunosuppressants. Despite their lack of structural similarities, CsA and FK506 have similar biological properties (Johansson et al., 1990, Transplant. 50:1001; Lin et al., 1991, Cellular Immunol. 133:269). Both molecules interfere with a T-cell receptor-mediated signaling pathway that results in the transcription of early T cell activation genes, although FK506 is able to do so at 100-fold lower concentrations (Tocci et al., 1989, J. Immunol. 143:718).